1. Field of the Invention
The present invention is related to a data transmitting device and a method for transmitting and receiving data and a data communication system.
2. Description of the Related Art
Communication techniques are known such as communication systems for use in limited areas such as vehicles in which devices are interconnected with a CAN (Controller Area Network) protocol as specified by OSEK (Offene System fund deren Schnittstellen fur die Elektronik im Kraftfahrzeug), ISO (International Standardization Organization) 15765 or the like. The CAN protocol is a serial communication protocol which is especially expected be used as a protocol for a vehicle network and is also expected to be used in medical or agricultural applications because of its high reliability.
In accordance with the communication techniques, when a plurality of terminals exchange data thereamong, the respective steps are performed as follows. When a data transmitting terminal has data to be transmitted to a data receiving terminal, the data transmitting terminal transmits first frame (FF) information to the data receiving terminal. In response, the data receiving terminal transmits a flow control (FC) frame to the data transmitting terminal. The flow control information includes separation time (STmin: separation time min) information indicative of the minimum interval between the successive frames transmitted, and block size (BS) information indicative of the number of frames which can be received. In this case, the block size information is indicative of the number of CAN frames in conformity with the CAN standard.
The data transmitting terminal transmits, to the data receiving terminal at a transmission interval in accordance with the separation time information, the number of CAN frames (CF: Consecutive Frame) compliant with the block size information included in the flow control information returned by the data receiving terminal.
After completely receiving the CAN frames, the data receiving terminal is enabled to receive next CAN frames and then returns flow control information to the data transmitting terminal which, in turn, performs again the transmission of CAN frames in accordance with the flow control information.
Data transmission from the data transmitting terminal to the data receiving terminal is performed by repeating these steps until no more data to be transmitted exists. In accordance with this type of communication technique, the data receiving terminal transmits, to the data transmitting terminal, information about the number of CAN frames which can be successively received and the minimum interval between the successive CAN frames in order to inform the data transmitting terminal of the memory capacity for receiving data and the speed for receiving data, so that the data transmitting terminal can perform the communication in compliance with the requirements of the data receiving terminal.